Gasoline internal combustion engine, with a combustion pre-chamber and two spark plugs

Abstract

An engine has, for each cylinder, a combustion chamber and a combustion pre-chamber communicating with the combustion chamber. First and second spark plugs are associated with the pre-chamber and combustion chamber, respectively. Gasoline is injected by an injector device directly into the combustion chamber and/or by an injector device into a cylinder intake duct. There is no device for injecting gasoline, air or an air/gasoline mixture directly into the pre-chamber. The engine operates with an air/gasoline mixture substantially corresponding to stoichiometric for compatibility with an exhaust system having a trivalent catalyst. The pre-chamber is, not used for engine operation with poor dosing, but to increase resistance to engine detonation. The engine can thus be configured with a high compression ratio, with a significant reduction in fuel consumption at the same power level. The second spark plug is only activated at low and medium engine loads to stabilize combustion.

Description

FIELD OF THE INVENTION[0001]The present invention relates to gasoline internal combustion engines, of the type comprising:[0002]an engine block with a plurality of cylinders and a cylinder head defining a combustion chamber associated with each cylinder, and at least one intake duct and at least one exhaust duct, provided with respective intake and exhaust valves, associated with each combustion chamber,[0003]a first spark plug associated with each cylinder, mounted within a support element that is arranged within a cavity of said cylinder head and that defines a combustion pre-chamber having a first end facing the electrodes of said first spark plug, and a second end communicating with the respective combustion chamber through a plurality of orifices,[0004]a second spark plug associated with each cylinder, having electrodes directly facing the combustion chamber,[0005]at least one electromagnetically-controlled gasoline injector device associated with each cylinder of the engine, a...

AI Technical Summary

Benefits of technology

[0012]A further object of the present invention is to provide an internal combustion engine of the above-mentioned type, which exhibits high detonation resistance and which can, therefore, be configured with a relatively high compression ratio, so as to allow, at equal power, a reduction of fuel consumption.

[0013]A further object of the present invention is to provide an internal combustion engine of the above-mentioned type, which has a simple structure with a reduced number of components and is consequently relatively inexpensive to produce.

[0014]A further object of the invention is to provide an internal combustion engine of the above-mentioned type, which allows modulation of the duration of combustion and that, in particular, at high loads, produces a rapid combustion in order to reduce the detonation tendency; at low loads and low engine speeds, it produces less rapid combustion, to reduce noise and that, in the heating steps, it also produces very long combustion to shorten the catalyst heating step, in order to reduce polluting emissions.

[0015]A further object of the invention is to provide an internal combustion engine of the above type, which also allows a significant temperature reduction to be obtained of the exhaust gases leaving the engine, at the same power, in order to reduce fuel consumption and emissions at high engine speeds and high loads, due to a lower enrichment of the charge required for the high temperatures of the engine components (particularly the turbocharger turbine, in the case of a supercharged engine).

Problems solved by technology

These known solutions are not compatible with conventional engine exhaust gas after-treatment systems using a trivalent catalyst, as typically used in ignition-controlled engines for motor-vehicle application.

Furthermore, the high surface / volume ratio of the combustion pre-chamber does not allow a safe and stable ignition, compatible with current emission regulations, at low temperatures.

The combustion pre-chamber is dimensioned to operate with lean mixtures, so that at high engine loads, the energy produced is too high and it is necessary to start combustion in the main combustion chamber and delay ignition in the combustion pre-chamber, to reduce the intensity of the jets leaving the combustion pre-chamber.

Similar problems are found in the document disclosed in U.S. Pat. No. 8,857,405 B2, which includes an active combustion pre-chamber, which is associated with a fuel injector, and a single spark plug associated with the combustion pre-chamber.

This known solution is also designed to operate with very lean mixtures and is not compatible with the use of a conventional trivalent catalyst.

Furthermore, the absence of the second spark plug does not allow stable operation or compliance with regulations concerning emissions at low temperatures and low loads.

Images